This application relates to the skateboard industry and specifically to skateboarding as a form of transportation, exercise, and high speed downhill skateboarding. During higher speeds, the skateboard operator typically travels longer distances and in a relatively straight line. Additionally, this skateboard provides a means of pumping to propel oneself, with quick turns, while remaining stable at higher speeds.
Some of the preferred embodiments include a skateboard with a truck similar to the cited prior art for steering, this truck will be referred to as a steering truck and another truck which is constrained to two degrees of freedom. The steering truck has offset axes which allow the skateboard to turn, and in some cases, provide propulsion. This propulsion is explained in prior art U.S. Pat. No. 8,454,038 O'Rourke column 6 lines 44 thru 54. The latter truck restricts the axle compliance to vertical displacement of each wheel independent of each other and rotationally about an axis perpendicular to this vertical displacement. The combination of this truck with the steering truck mentioned above, uniquely allows for propulsion and stability at higher speeds.
Current solutions exist addressing the instability. One solution is referred to as a zero angle truck and is specifically designed with a pivot angle of zero degrees. However, this solution relies on the skateboard platform to provide all structural support. By providing both structure and the compliance needed for performance, this invention eliminates weight, complexity and cost from the skateboard system.
Also noteworthy is that the bushings that provide spring back in this traditional truck type of design are mechanically disadvantaged as the pivot angle goes to zero and is prone to wear more quickly when the deck is tilted repeatedly for turning.
It has been found that at higher speeds the axle in the steering truck can start to oscillate about a vertical axis causing the steering truck to turn back and forth in an uncontrollable manner. One can understand that if all trucks on the skateboard are allowed to react in this fashion the operator would tend to lose control. Therefore, understanding this undesired problem the inventor has provided a truck which allows a steering truck to operate as required for control but reduces steering within its own mechanics, thus providing a more stable experience especially at higher speeds.
An embodiment includes a rear axle which is compliant in two degrees of freedom. This compliance is characterized with flex and spring in the degrees of freedom. One embodiment includes an axle support that has vertical compliance and rotational compliance about an axis parallel to the direction of travel. The approximate location and orientation of these degrees of freedom will be discussed in more detail below. Additionally, the rotational degrees of freedom are described as having directions in the form of vector components this will be explained in more detail with reference to FIG. 7 in the detailed description.
The prior art cited in U.S. Pat. No. 8,454,038 O'Rourke teaches a bidirectional propulsion caster assembly which enables a rider to generate bi-directional motion from a ride-on device (page 1 abstract). This patent teaches the benefits of an angularly offset wheel axis as stated in column 4 line 41 thru 43 of the detailed description. This patent goes on to tout the ability of the offset axis to create an obtuse or acute angle of the caster shaft, see column 5 line 3 thru 13 of the detailed description. It is understood that this device also has an undesirable axle oscillation effect at higher speeds.
Other prior art is cited which includes U.S. Pat. No. 7,341,260 Hosoda. This patent teaches a single offset axis arrangement and the use of a torsion spring. This torsion spring is situated such that it prevents jamming of the offset axis during steering of the skateboard. As stated in the detailed description, the rotational axis of the wheels and the offset axis connected to the base of the skate board are not perpendicular to the plane of the base, see column 2 lines 45 thru 54. This truck device is understood to have stability issues at higher speed, caused again, by axle oscillation.
FIGS. 23, 24, 25 and 26 shows a zero degree truck 100. The zero degree truck 100, allows the axle 104 to pivot about an axis 101. FIG. 24 shows the axle 104 which is supported by the axle housing 105. Each end of the axle 104 has two bearings 103A, 103B, 103C and 103D; these bearings support the wheels 102A and 102B in the usual manner.
FIG. 25 shows a vertical pin 107 which is supported by compliant bushings 106A and 106B and also is rotationally attached to the axle housing 105. The axle housing 105 supports the axle 104. By twisting the base 110, the compliant bushings 106A and 106B are loaded against the pin 107, the axle housing 105 and the washer 109. The axle housing 105 includes a pivot support feature 105A which allows the axle housing 105 to pivot inside a wear bushing 108. In this embodiment the spring back function resisting the twisting is provided by twisting the compliant bushings 106A and 106B. This device however does not reduce cost, decrease the weight and does not provide for strong spring back characteristics. For instance as the compliant bushings 106A and 106B wear the spring back function is adversely effected causing for a less enjoyable experience.
Other prior art exists which includes the use of a skateboard truck that is modified to prevent the wheels from turning as the base is twisted. No actual documentation is available; however, this type of truck is very similar to the truck of U.S. Pat. No. 7,341,260.
Many of the above cited prior art includes skateboard trucks that include two pivoting axes that require additional hardware. This additional hardware has some undesirable consequences such as increased cost and weight and tended to increase the height of the skateboard base. The increased height of the base has been determined to cause a less comfortable experience for the user.
Another problem with the cited prior art is the response of the skateboard to “spring back” to the untwisted or horizontal orientation. This spring back is addressed in cited prior art of U.S. Pat. No. 7,341,260 to Hosoda. This patent teaches the inclusion of a spring (labeled item 22) which provides spring back into a horizontal position of the skateboard base.
The instant invention addresses the stability, spring back, cost and weight issues of the above prior art. Many of the embodiments combine spring back and compliance into the structure of the skateboard base. This is accomplished by structural members instead of additional pivoting mechanisms. The use of these compliant structural members increases the overall higher speed skateboarding experience. Additionally, the trailing wheels are positioned away from the trailing end of the skateboard base such that the wheels do not contact the base even during maximum compliance. This interference is typically referred to as “wheel bite”.
Some of the preferred embodiments address the issue of stability at higher speeds of a skateboard that allows steering and propulsion. Additionally, each and every issue in the prior art is not addressed by each embodiment. In fact, some embodiments may not address any of the prior art issues mentioned above.